I'm going to replace the rubber seal on the rear windshield of my '81 240D. I'm going to use the service manual CD. However, according to the CD, after I install the window with the new seal, I need to apply MB Window Sealing Compound. I contacted the local MB dealership and they said it would have to be ordered from Germany and that the cost is $22.50! My question is, is there any other readily available sealing compound I can use?

Also, how much does the rear windshield weigh?